Nonaqueous electrolyte secondary batteries, particularly lithium-ion secondary batteries, have a high energy density, and are therefore in wide use as batteries for personal computers, mobile telephones, portable information terminals, and the like. Such nonaqueous electrolyte secondary batteries have recently been developed as on-vehicle batteries.
As a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery which includes a porous film containing a polyolefin as a main component as disclosed in Patent Literature 1 is, for example, known.